Metal plating on nonconductive substrates

ABSTRACT

A METHOD OF INCREASING THE EFFECTIVE STRENGTH OF ELECTROLESS AND/OR ELECTROLYTIC METAL PLATE ADHESION T A NONMETALLIC SUBSTRATE WHICH COMPRISES THE INCORPORATION IN THE METAL PLATE OF AT LEAST ONE LAYER OF METAL SO MODIFIED THAT THE TOTAL PLATE HAS A FLEX STRENGTH NOT GREATER THAN EITHER THE COHESIVE STRENGTH OF THE SUBSTRATE, OR THE ADHERENT BOND STRENGTH OF THE METALLIC PLATE TO THE SUBSTRATE.

United States Patent Int. Cl. C231) 5/60 U.S. Cl. 204-30 64 Claims ABSTRACT OF THE- DISCLOSURE- BACKGROUND OF THE INVENTION There is a rapidly increasing demand for metal plated articles, for example, in the production of low-cost plastic articles that have a metallic function and appearance. Such articles are in demand in such industries as automotive, home appliance, radio and television and for use in decorative containers and the like.

Heretofore, the electroless and/or electrolytic metal plating of nonmetallic substrates has had limited application due to the difliculty of forming an adherent bond between the substrate and the metallic coating. Though several processes for electroless and/or electrolytic metal plating on nonmetallic substrates have been explored, they generally suffer a disadvantage in that the metal plate can be peeled off the surface, especially in the case of thermosetting resins. Great emphasis has been placed on attaining a method of electroless and/or electrolytic metal plating of nonmetallic substrates which results in a nonpeeling product. Prior art methods have sought to attain this product by strengthening the adherent bond between the substrate and metal layer. Improved plating techniques and compositions have resulted in stronger adherent bonds, but there are limits to which improvements in bond strength can be obtained.

It 'has been found that three factors lend most significance to metal plate peeling: the flex strength of the metal plate, the cohesive strength of the substrate, and the adherent bond strength of the metallic plate to substrate. Prior art methods of eliminating peel have centered about the importance of a strong adherent bond. It has been found however, that if the flex strength of the metal plate exceeds the cohesive strength of the substrate, peeling can occur regardless of the strength of the adherent bond. If the flex strength is greater than the cohesive strength and the adherent bond strength is less than the cohesive strength of the substrate, peeling will occur at the bond; if the adherent bond strength exceeds the cohesive strength of the substrate, peeling will occur beneath the surface of the substrate.

It is an object of this invention to provide an improved process for the metallic coating of nonmetallic substrates. It is also an object of this invention to provide an improved process for metallic coating of nonmetallic substrates wherein the resulting metal plated substrate has an increased effective peel strength. A further object of this invention is to provide for a metal coated nonmetallic substrate having a combination of flexibility, high effective peel strength and good aesthetic appearance. These and other objects will-become apparent to one skilled in the art of the following disclosure.

3,681,209 Patented Aug. 1, 1972 SUMMARY OF THE INVENTION Accordingly, the present invention provides a method of increasing the effective strength of electroless and/or electrolytic metal plate adhesion to a nonmetallic substrate which comprises the incorporation in the metal plates of at least one layer of metal so modified that the total plate has a flex strength not greater than either the cohesive strength of the substrate, and the adherent bond strength of the metallic plate to the substrate. The invention also resides in the resulting plated articles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of this invention is applicable to substrates, such as plastics and to other substantially non-metallic substrates. Suitable substrates in addition to plastics include, but are not limited to, cellulosic and ceramic materials such as cloth, paper, woods, cork, cardboard, clay, porcelain, leather, porous glass, asbestos, cement, and the like.

Typical plastics to which the process of this invention is applicable include the homopolymers and copolymers of ethylenically unsaturated aliphatic, alicyclic and aromatic hydrocarbons such as polyethylene, polypropylene, polybutene, ethylenepropylene copolymers; copolymers of ethylene or propylene or with other olefins, polybutadiene; polymers of butadiene, polyisoprene, both natural and synthetic, polystyrene including high impact polystyrene, and polymers of pentene, hexene, heptene, octene, 2- methylpropene, 4 methyl hexene-l, bicyclo-(2.2.1)-2- heptene, pentadiene, hexadiene, 2,3-dimethylbutadienc- 1,3,4-vinylcyclohexene, cyclopentadiene, methylstyrene, and the like. Other polymers useful in the invention include polyhalogenated hydrocarbon polymers, including fluoro polymers such as polytetrafluoroethylene; polysilicone and polyhalogenated silicones; polyindene, indenecoumarone resins; polymers or acrylate esters and polymers of methacrylate esters, acrylate and methacrylate resins such as ethyl acrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl methacrylate and methyl methacrylate; alkyl resins; cellulose derivatives such as cellulose acetate, cellulose acetate butyrate, cellulose nitrate, ethyl cellulose, hydroxyethyl cellulose, methyl cellulose and sodium carboxymethyl cellulose; epoxy resins, furan resins (furfuryl alcohol or furfuralketone); hydrocarbon resins from petroleum; isobutylene resins (polyisobutylene); isocyanate resins (polyurethanes); melamine resins such as melamine-formaldehyde and melamine-urea-formaldehyde; oleo resins; phenolic resins such as phenol-formaldehyde, phenolic elastomer, phenolic epoxy, phenolic-polyamide, and phenolic-vinyl acetals; polyamide polymers, such as polyamides, polyamide-epoxy and particularly long chain synthetic polymeric amides containing recurring carbonamide groups as an integral part of the main polymers chain; polyacryl amides; polysulfones; polyester resins such as unsaturated polyesters of dibasic acids and dihydroxy compounds, and polyester elastomers and resorcinol resins such as resorcinolformaldehyde, resorcinol furfural, resorcinol phenolformaldehyde, resorcinol-polyamide and resorcinol-urea; rubbers such as natural rubber, synthetic polyisoprene, reclaimed rubber, chlorinated rubber, polybutadiene, cyclized rubber, butadiene-acrylonitrile rubber, butadienestyrene rubber, and butyl rubber, neoprene rubber (polychloroprene); polysulfides (Thiokol); terpene resins, urea resins; vinyl resins such as polymers of vinyl acetal, vinyl acetate or vinyl alcohol-acetatev copolymers, vinyl alcohol, vinyl chloride, vinyl butyral, vinyl chlorideacetate copolymer, vinyl pyrrolidone and vinyldene chloride copolymer; polyformaldehyde; po lyethers, such as polyphenylene oxide, polymers of diallyl phthalates and phthalates; polycarbonates of phosgene or thiophosgene and dihydroxy compounds such as bisphenols, thermoplastic polymers of bisphenols and epichlorohydrin (trademane Phenoxy polymers); graft copolymers and polymers of unsaturated hydrocarbons and an unsaturated monomer, such as graft copolymers of polybutadiene, styrene and acrylonitrile, commonly called ABS resins; ABS-polyvinyl chloride polymers; acrylic polyvinyl chloride polymers; and any other suitable natural and synthetic polymers.

The polymers of the invention can be used in the unfilled condition, or with fillers such as glass fiber, glass powder, glass beads, asbestos, talc and other mineral fillers, wood flour and other vegetable fillers, carbon in its various forms, dyes, pigments, waxes and the like.

The process of this invention is applicable to the electrolytic and/or electroless processes for metal plating of nonconductive substrates. A typical process of this invention includes the treatment of the nonconductive substrate with an electroless preplate process so as to deposit an electroless metal plate or strike and then electrolytically plating metal thereon.

The nonmetallic substrates of the invention are first subjected to a preplating process wherein the surface of the substrate is rendered active, catalytically or conductively so as to allow metal deposition. The manner of activation of the surface, i.e., whether there is an intermingling of charged or conductive particles or molecules, whether an activated coating is applied, or whether the surface molecules are rendered conductive is not controlling.

Typical preplate process include processes comprising basically three separate preparation steps. These steps include (1) pretreating of the substrate surface, such as (a) etching the substrate with various acidic solutions to produce very small holes, pores and channels in the surface, and (1)) treatments of the substrate with a solvent, in either case to provide anchoring sites for subsequent electrodepositing, (2) sensitizing of the etched surface with various sensitizing solutions and/or (3) activation of the substrate surface by treatment with a metal salt solution. Additional solutions or steps may be included in these systems in order to improve reliability or extend the range of performance.

'One embodiment of the above process comprises 1) etching the substrate with a solution of CrO and H SO with or without the addition of H PO (2) sensitizing the etched surface with a stannous chloride sensitizing solution and/or (3) activating the substrate surface by treatment with a metal salt solution, and thereafter (4) subjecting the thus treated substrate to an electroless metal solution for electroless metal deposition. Such a process is disclosed in U.S. Pat. 3,235,473 which is incorporated herein by reference.

A second embodiment of the above process comprises activating the etched surface with a solution of Li PdCl, in methanol, treating the activated surface with a solution of NaH PO in water and/or subjecting to an electroless metal solution for electroless metal deposition, which is disclosed in a pending application Ser. No. 52,714, filed July 6, 1970, and now abandoned, and is hereby incorporated by reference. This process can be modified by pre-etching the substrate with a solution of CrO and H 80, which is the invention of Chong-tan Liu.

A third embodiment of the above process comprises activating the etched surface with a solution of white phosphorus and sodium in ethanol solution and thereafter subjecting the treated surface to an electroless metal solution for electroless metal deposition, as disclosed in copending application Ser. No. 839,080, filed July 3, 1969 which is hereby incorporated herein. This process can be modified by pre-etching the substrate with a solution of CrO and H 80 which is the invention of Chong-tan Liu.

A fourth embodiment of the above process comprises (1) treating the nonconductive substrate with a solution of Na S as is disclosed in U.S. 3,523,875 which is incorporated herein by reference, and thereafter activating the substrate with a solution of PdCl in HCl. This process can be modified by subjecting the thus activated substrate to an electroless metal solution for electroless metal deposition which is the invention of Chong-tan Liu.

A fifth preplate process provides for the treatment of the substrate with elemental white phosphorus andthereafter with a metal salt or complex thereof. This process is described in copending application Ser. No. 614,541, filed Feb. 8, 1967, which disclosure is incorporated herein by reference.

Still another method involves subjecting the substrate to low oxidation state phosphorus compounds and thereafter to a metal salt or complex thereof. Such processes are disclosed in copending applications Ser. No. 750,488, filed Aug. 6, 1968, and now abandoned, and Ser. No. 750,477, filed Aug. 6, 1968, and now abandoned, which disclosures are hereby incorporated by reference.

The method and composition of electroless and/or electrolytic plating of the surface activated substrate determines the flex strength of the metal plated layer, therefore, any process that produces a metal plate flex strength which is not greater than the cohesive strength of the substrate or the adherent bond strength of the metallic plate to the substrate is operable herewith.

Typical processes, wherein the flex strength of the metal plated layer is reduced so as not to be greater than cohesive strength of the substrate or the adherent bond strength of the metallic plate to the substrate comprise micro-cracking processes, the codeposition of occluded particles, and processes wherein the metal layer is otherwise treated to impart a low flex strength. The article to be plated is generally used as the cathode. The metal desired to be plated is generally dissolved in an aqueous plating bath, although other media can be employed. Generally, a soluble metal anode of the metal to be plated can be employed. In some instances, however, a carbon anode or other inert anode is used. Suitable metals, solutions and condition for electroplating are described in Metal Finishing Guidebook Directory for 1967, published by Metals and Plastics Publications, Inc., Westwood, NJ.

Microcracking processes operable herewith, typically include those processes wherein a network of cracks, microscopically resolvable has been induced in at least one of the metal layers so that the flex strength of the total metal plate is less than the cohesive strength of the substrate or the adherent bond strength of the metallic plate to the substrate. Composite metal deposition in high chloride electrolytic baths, causes a porous and finely micro-cracked structural pattern to develop. The deposition of the above described micro-cracked layer weakens the flex strength of the deposited metal layer so that it is less than the cohesive strength of the substrate or the adherent bond strength of the metallic plate to the sub strate. The resulting plated substrate has excellent esthetic appearance and cannot be peeled. An embodiment of this plocess is described in U.S. Pat. 3,471,271, which disclosure is hereby incorporated by reference, wherein the high chloride plating both additionally contains an amino acid. A porous and finely microcracked structural pattern may additionally be caused to develop in metal plate by the use of selenic acid in the chromium plating bath. Typical embodiments and results of this process are described in the article Advances in Electroplating Decorative, Microcracked Chromium, June 1964, Plating Magazine, which disclosure is hereby incorporated by refer ence.

A second process which is useful in this invention, comprises the co-deposition of fine particles with the electroless or electrolytically deposited metal layer. In such processes, the particles are occluded within the metal plate, so as to weaken the flex strength thereof. A typical embodiment of this process provides for the co-depositionof fine powders having in general, a particle size of less than microns in diameter and preferably less than 2 microns. U.S. Pats. 3,152,971, 3,152,972 and 3,152,973, which disclosures are hereby incorporated by reference, describe processes. wherein nickel plating baths are respectively modified by adding thereto fine powders of various oxides, carbides, silicides, nitrides, fluorides, and sulfides, such as silicon carbide, boron carbide, titanium carbide, silicon dioxide, manganese oxide, titanium oxide, zirconium oxide, aluminum oxide, ceric oxide, ferric oxide, chromic oxide, boron nitride, calcium fluoride, strontium fluoride, borium fluoride, zinc sulfide, cadmium sulfide and iron silicide; bath insoluble silicates of aluminum, magnesium, boron, calcium, strontium and barium, and the mixed silicates of these metals such as barium alumino silicate, and including the insoluble silicates containing alkali metals; and sulfates, carbonates, phosphates and oxalates of the alkaline earth metals, barium, strontium and calcium.

Further typical embodiments of the above process which are operable herewith are as disclosed in U.S. Pats. 3,268,307, 3,268,423 and 3,268,424, which disclosures are hereby incorporated by reference, wherein nickel plating baths are modified by the addition of water-insoluble fine powders of boron, silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium, vanadium, the carbides of chromium, vanadium, tungsten, and zirconium, the nitrides of silicon, titanium and zirconium, and the silicides of titanium, zirconium, nickel, cobalt, and cerium, the phosphides of chromium, tungsten, molybdenum, manganese, nickel, cobalt, iron, cerium, titanium, zirconium and vanadium, and the oxides of thorium and stannic tin, including hydrated stannic oxide (meta stannic acid); barium chromate, lead chromate, phosphates of thorium and lead, the oxides and hydroxides of nickel and cobalt, and the stannates of calcium, strontium, barium, lead, nickel, cobalt and iron; and compound metals having incomplete inner electron shells, such as the metals of the transition series, the metals of the Lanthanide or rare earth series, and of the actinide series.

A typical embodiment of the above process is also disclosed in US. Pat. 3,268,308, which disclosure is hereby incorporated by reference, wherein inorganic oxygencontaining titanium and zirconium compounds are added to nickel plating baths so as to occlude particles within the metal plate. Additionally, US. Pat. 3,356,467, which disclosure is hereby incorporated herein by reference, discloses the modification of a nickel and nickel alloy bath by the addition therein of fine bath-insoluble organic resins, a process operative in the instant invention.

Additionally, other processes which produce low flexural strength, electrolytically deposited metal plate, are effective in that the flex strength is reduced below the cohesive strength of the substrate or the adherent bond strength of the metallic plate to the substrate. Typically, processes wherein aromatic and aliphatic amines are added to the electrolytic bath cause brittleness and especially preferred, with the least effect on adherent bond strength, are the addition of polyethylene glycols having a molecular weight of about 300 to about 5,000 and polypropylene glycols having a molecular weight from about 300 to about 1,000. 0f the amines, nicotinic acid appears to have the least effect on substrate to metal plate adherency, while causing a brittle plate.

The following examples are listed to show some preferred processes useful in obtaining a metal plated, nonconductive substrate, wherein the metal layer has a flex strength which is less than or equal to the cohesive strength of the substrate or the adherent bond strength of the metallic plate to the substrate.

Where indicated, the metal plated substrate was subjected to standard testing techniques so as to determine metal plate adhesion characteristics. None of the plated substrates, prepared as to the process of the instant invention, could be peeled by the standard J acquet test method,

i.e., the metal could not be peeled in ductile layers. To obtain an evaluation of the metal to substrate bond, the metal coating was cross-hatched in Va" x 4;" squares and evaluated as to its resistance to gouging and lifting with a knife. The thus determined resistance was termed effective adhesion and was numerically scaled from 0 to 3, defined as follows:

0--No elfective adhesion, the metal plate readily lifts off the substrate.

1-Some elfective adhesion, the metal plate lifts but with partial breaking.

2-Fair effective adhesion, the metal plate could be only partially lifted and with difiiculty. Additionally, the metal plate was subject to extensive breaking.

3Excellent effective adhesion, the metal plate could not be lifted.

Example 1 An article made of flock-filled, one-step phenol-formaldehyde, thermosetting molding compound, was contacted with a solution containing 351 g./l. CrO and 210 mL/l. conc. H SO for 6 minutes at C. so as to form an acid etch on its surface. The etched article was thereafter rinsed in tap Water, and sensitized for 2 minutes in a solution containing 86 g./l. SnCl -H O and 89 ml./l. conc. HCl. The sensitized article was then rinsed in tap water and contacted for 2 minutes with an activating solution containing 1 g./. PdCl .H O and l mL/l. conc. HCl. The thus surface activated article was thereafter subjected to electroless nickel deposition for 10 minutes at a pH of 4.5 and a temperature of 88 C. in the following electroless metal solution:

55.6 g. NiCl -6H O 18.5 g. NaH PO -H O 18.5 g. Na.citrate 0.002 g. Pb(Ac) 1855 ml. water The resultant preplated article was thereafter rinsed in tap water and air dried.

Example 2 An article made of the molding compound of Example 1 was contacted with a solution containing 351 g./l. CrO and 210 ml./l. conc. H SO for 6 minutes at 80 C. so as to form an acid etch on its surface. The etched article was thereafter rinsed in tap water, oven dried at 65 C. for 3 0 minutes, and thereafter sensitized for 2 minutes in a solution of 0.0625 g. Li 'PdCl per liter CH OH. The thus sensitized article was then air dried for 1 minute then activated in a solution of 15 g. NaH PO /LH 0 for 1 minute. The surface activated article was then subjected to electroless nickel deposition for 1 0 minutes at a pH of 4.5 and a temperature of 88 C. in the electroless metal solution of Example 1. The preplated article was thereafter rinsed in tap water and air dried.

Example 3 An article of the molding compound of Example 1 was contacted with an 18% Na 'S solution at C. for 5 minutes. The article was thereafter rinsed in tap water and activated by contacting it with a solution containing 1 g./l. PdCl and 1 ml./l. conc. HCl for 2 minutes. The surface activated article Was then rinsed in tap water and subjected to electroless nickel deposition for 10 minutes at a pH of 4.5 and a temperature of 85 C. in the electroless metal solution of Example 1. The preplated article was thereafter rinsed in tap water and air dried.

Example 4 An article made of the molding compound of Example 1 was contacted with a solution containing 351 g./1. CrO and 210 ml./l. conc. H SO for 6 minutes at 80 C. so as to form an acid etch on its surface. The etched article was thereafter rinsed in tap water, oven dried for 20 minutes at 55 C., and thereafter activated in a solution containing (0.007 m. P '+0.028 m. Na) per liter The activated article was then air dried for 5 minutes at room temperature and subjected to electroless nickel deposition for minutes at a pH of 4.5 and a temperature of 88 C. in the electroless metal solution of Example 1. The preplated article was thereafter rinsed in tap water and air dried.

Example 5 Example 6 The preplated article of Example 1 was electrolytically metal plated in accordance with the instant invention. A 0.5 mil micro-cracked metal under layer was electrolytically deposited thereon using the following components and conditions:

NiCl -6H O 350 g./l. ;H BO 3 0 g./l. Nicotinic acid 1 g./l.

pH 1. Temperature 72 F. Agitation Air.

Current 70 amps/ftfi.

Thereafter, a standard composite upper layer of 0.4 mil semi-bright nickel, 0.4 mil bright nickel and a flash of chromium was electrolytically deposited thereon. The thus deposited metal coating was tested for peeling and effective adhesion. The metal layer would not peel, and had an effective adhesion of 3.

Example 7 The preplated article of Example 2 was electrolytically metal plated in accordance with Example 6. The metal layer thus formed would not peel and had an effective adhesion of 2.

Example 8 The preplated article of Example 3 was electrolytically metal plated in accordance with Example 6. The metal layer would not peel and had an eflective adhesion of 1.

Example 9 An article of a glass-filled, alkyd resin thermosetting molding compound was preplated in accordance with Example 1. Thereafter, the preplated article was electrolytically metal plated in accordance with Example 6. The metal layer thus formed would not peel and had an effective adhesion of 1.

Example 10 The preplated article of Example 1 was electrolytically metal plated in accordance with the instant invention. A 0.5 mil metal under layer was electrolytically deposited thereon using the following components and conditions:

NiCl -6H O 350 g./1. NiSO -6H 0 40 g./l. 0 'H 'BO g./l. Na-ethylenediaminetetraacetate 25 g./l. Temperature 72 F. Agitation Air. Current 70 amps/ft. {75

8 Thereafter, a standard composite upper layer of 0.4 mil semi-bright nickel, 0.4 mil bright nickel and a flash of chromium Was electrolytically deposited thereon. Upon subjecting to the aforementioned testing procedure, the metal layer would not peel and had an effective adhesion of 2. v

Example 11 The preplated article of Example 4 was electrolytically metal plated in accordance with Example 10 with the exception that the current usedfor deposition of the under layer was 70 amps/ftfi. The metal layer would not peel and had an effective adhesion of 1.

' Example12 The preplated article of Example 2 was electrolytically metal plated in accordance with the instant invention. A 0.5 mil metal under layer was electrolytically deposited thereon using the following components and conditions:

NiC1 -6H O 350 g./l. NiSO -6H O g./l. H BO 25'g./l. Hydroxyethylethylene diaminetriacetic acid Do. Na-ethylene diaminetetraacetate Do. Temperature 72 F. v I Agitation Air. Current 1 00 amps./ft.

Thereafter, a standard composite upper layer of 0.4 mil semi-bright nickel, 0.4 mil bright nickel and .a flash-of chromium was electrolytically deposited thereon. Upon subjecting to the aforementioned testing procedure, the metal layer would not peel and had an effective adhesion of 2.

Example 13 The preplated article of Example 1 was electrolytically metal plated in accordance with the instant invention. A 1.0 mil metal under layer was electrolytically deposited thereon using the following components and conditions:

NiSO '6I-I O 300 g./l. NiCl -6H O so g./l. H3B03 4s g /l. Baso, 15o g./l.

Saccharin 2-3 g./l. Adduct of 1 to 2 moles of ethylene oxide with 1 mole of butylene diol 0.05-0.15 g./l. Temperature 72 F. Agitation Mechanical stirring. Current 70 amps/ft?- Thereafter, a standard composite upper layer of 0.1 and semi-bright nickel, 0.1 mil bright nickel and a flash of chromium was electrolytically deposited thereon. Upon subjecting to the aforementioned testing procedure, the metal layer would not peel and had an elfective adhesion of 3.

Example 14 The preplated article of Example 2 was electrolytically metal plated in accordance with Example 13, with the exception that the current used for deposition of the under layer was amps/ftF. The metal'layer would not peel and had an eifective adhesion of 2. 1

Example 15 The preplated article of Example 3 was electrolytically metal plated in accordance with Example 14. The metal layer would not peel and had an effective adhesion of 1.

Example 16 An article made of a general purpose mineral-filled, alkyd resin thermosetting molding compound was preplated in accordance with Example 1 and thereafter electrolytically metal plated in accordance with Example 14. The'metal layer-would not peel and had an etfe'ctivexadhesionof'l. I

" Example -.17-

The preplated article of Example 1 was electrolytically metal plated in accordance with the'instant invention. A 1.0 mil metal under layer was electrolytically deposited thereon using the following components and conditions:

NiCl -6H O 3'50 g./l.

NiSO -6I-I' O 40 g./l.

H3BO3 g./l.'

Na-ethylene: diamine tetraacetate 25 g./l.

Temperature -Q 72 F.

Agitation Mechanical stirring.

Current. 50 amps/ftfi.

Thereafter, a standard composite upper layer of 0.1 mil semi-bright nickel, 0.1 mil bright nickel and a flash of chromium was electrolytically deposited thereon. Upon subjecting to the aforementionedtesting procedure, the metal'layer would not peel and had an elfective adhesion of3. 1

Example 18 The preplated article of Example 4 was electrolytically metal plated in accordance with Example '17. The metal plated layer would not peel and had an effective adhesion of 3.

Example 19 The preplated article of Example 1 was electrolytically metal plated in accordance with the instant invention. A 1.0 mil metal under layer was electrolytically deposited thereon-using the following components and conditions:

Thereafter a standard composite upper layer of 0.1 semi-bright nickel, .0.1 mil bright nickel and a flashof chromium was electrolytically deposited thereon. Upon subjecting to the, aforementioned testing procedure, the

metal layer would not peel and had an effective adhesion of 3.

Example 20 The preplated article of Example 1 was electrolytically metal plated in accordance with the instant invention.

A 0.5 mil metal layer was electrolytically deposited thereon using the following components and conditions:

CrO g /l 250 H 80 '(conc.) "Q 'g./l 1.5 HgSiFg .g./l Na SeO g /l 15 Temperature C-.. 47 Current amps/ft. 135

Upon subjecting tothe aforementioned testing procedure,

the metal layer would not peel and had an etfective' adhesion of 3.

Example 21 The preplated article of Example 1 was metal plated according to the instant invention. A 0.5 mil metal'under 10 layer was electrolessly deposited thereon using the following components and conditions:

NiCl -6H O L... 55 .6 g. NaH PO -H o 1s.'5 g.

Na-cit-rate 18.5 g.

Pb-acetate 0.0022 g.

BaSO 300.0 g.

H O 1855 ml.

Temperature f 82 C. I Agitation Mechanical stirring.

Thereafter, a standard upper layer of 0.1 mil semi-bright nickel and a flash of chromium was electrolytically deposited thereon. The metal layer would not peel-and had an eifective adhesion of 3.

Example 22 An article made of a mineral and flock-filled, two-step phenol-formaldehyde thermosetting molding compound, was preplated in accordance with Example 1 with the exception that the etching process was extended to 15 minutes. The thus prepaltedarticle was electroyltically metal palted in accordance with Example 6. Upon subjecting to the aforementioned test procedure, the metal layer would not peel and had an effective adhesion of 3.

Example 23 An article made of a mineral and cellulose filled, twostep phenol-formaldehyde thermosetting molding compound was metal plated in accordance with Example 22. The metal layer would not peel and had an effective adhesion of 3.

Example 24 An article made of a general purpose polypropylene compound was contacted with a solution of one percent elemental phosphorus in trichloroethylene for 1 minute at 35 C. and thereafter air dried for one minute. The thus treated article was then subjected for 15 minutes at 65 C. in the following aqueous solution:

M. NiCl 0.04 Ethylenediamine 0.16 NaOH 0.18

The preplated article was thereafter rinsed in tap water and oven dried for 30 minutes at 65 C. Thereafter, the preplated article was electrolytically metal plated by the method of Example- 6, at a current density of amps/ ft.. The metal layer would not peel, and had an efiective adhesion of 3.

- Example 25 An article made of a linear polyester polyurethane film, was pretreated with methanol for.2 minutes at 35 C., air dried for one minute, and thereafter subjected to a solution of 1% P 8 in perchloroethylene solution for 10 minutes at 35 C. The thus treated article was thereafter preplated for 15 minutes at 60 C. with the following aqueous solution:

CuCl 0.04 Ethylenediamine 0.16 NaOH' 0.32

The preplated article was thereafter rinsed in tap water for one minute and oven dried.

Example 26 The preplated article of Example 25 was thereafter electrolytically metal plated by the method of (Example 6, at a current density of 50 amps/ftfl. The metal layer would not peel, and had an effective adhesion of 3.

Example 27 Articles made of polyvinyl chloride, a general purpose polypropylene compound; a general service, high modulus, natural color, acrylonitrile-butadiene-styrene (ABS) compound; and a standard natural color, low density polyethylene sheet; were preplated by the method of Example 25 and thereafter electrolytically metal plated by the method of Example 6, wherein equivalent results were obtained.

Example 28 Articles made of ABS, a polyvinyl chloride lfilm; were preplated by the method of Example 25 and thereafter electrolytically metal plated by the method of Example 13, wherein equivalent results were obtained.

Various changes and modifications can be made in the process and products of this invention, without departing from the spirit and scope of the invention. The various embodiments of the invention disclosed herein serve to further illustrate the invention but are not intended to limit it.

Throughout this specification and claims, parts are expressed by weight and temperatures in degrees centigrade unless indicated otherwise.

We claim: g

1. A method for applying an adherent metal coating to a nonmetallic substrate having a conductive surface thereon: comprising electrolytically depositing on said conductive surface a metallic plate having a flex strength that is not greater than either the cohesive strength of said substrate or the adherent bond strength of the metallic plate to said substrate.

2. The process of claim 1 wherein a glycol is present in the electrolytic bath in an amount sufiicient to produce embrittlement of the electrolytically deposited metal plate.

3. The method of claim 1 wherein aromatic or aliphatic amines are present in the electrolytic bath in an amount sufficient to produce brittleness of the electrolytically deposited metal plate.

4. A method according to claim 1 for applying an adherent metal coating to a nonmetallic substrate comprising treating said substrate to provide a conductive surface thereon, and electrolytically depositing on said conductive surface a metallic plate having a flex strength that is not greater than either the cohesive strength of said substrate or the adherent bond strength of the metallic plate to said substrate.

5. The method of claim 1 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding fine, inert particles, of less than 5 microns, in the metal plate.

6. The method of claim 5 wherein said particles are co-deposited with the electrolytic metal plate.

7. The method of claim 1 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

8. The method of claim 7 wherein the microscopically resolvable network of cracks is producedby conducting the electrolytic metal deposition in an electrolytic bath having a high chloride ion content, of 150-500 g./l. nickel chloride.

9. The method of claim 7 wherein nicotinic acid is present in the electrolytic bath in an amount suflicient to produce microscopically resolvable cracks in the electrolytically deposited metal plate.

10. A method according to claim 1 for applying a adherent metal coating to a non-metallic substrate comprising treating said substrate with white phosphorous and sodium in ethanol solution, subjecting the thus treated substrate to an electroless metal solution for electroless metal deposition and thereafter electrolytically depositing thereon a metallic plate having a flex strength that is not greater than either the cohesive strength of said'substrate or the adherent-bond strength of the metallic plate-to said substrate.

. 11. The method of claim 10 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding therein fine inert particles, of less than 5 12 microns, co-deposited with the electrolytically deposited metal plate.

12. The method of claim 11 wherein the metal plate is nickel.

13. The method of claim 11 wherein the substrate is a plastic.

14. The method of claim 10 wherein the substrate is pretreated with a solution of CrO and H 50 15. The method of claim 14 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

16. The method of claim 15 wherein the metal plate is nickel.

17. The method of claim 15 wherein the substrate is a plastic. 1

18. A method according to claim 1 for applying an adherent metal coating to a nonmetallic substrate comprising treating said substrate with a solution of Na s, activating the thus treated substrate with a solutionv of PdCl in aqueous hydrogen chloride, and thereafter electrolytically depositing on the activated substrate a metallic plate having a flex strength that is not greater than either the cohesive strength of said substrate or the adherent bond strength of the metallic plate to said substrate.

19. The method of claim 18 wherein the activated substrate is subjected to an electroless metal solution for electrolytic. metal deposition prior to electrolytic metal deposition.

20. The method of claim 18 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

21. The method of claim 20 wherein the metal plate is nickel.

22. The method of claim 20 wherein the substrate is a plastic.

23. The method of claim 18 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding therein fine inert particles, of less than 5 microns, co-deposited with the electrolytically deposited metal plate.

24. The method of claim 23 wherein the metal plate is selected from the group consisting of nickel and chromium.

25. The method of claim 23 wherein the substrate is a plastic.

26. A method according to claim 1 for applying an adherent metal coating to a nonmetallic substrate comprising subjecting said substrate to a member of the group consisting of elemental phosphorus and low oxidation state phosphorus compounds wherein phosphorus has a valence below 5, subjecting the thus treated substrate to a metal salt or complex thereof, wherein said metal is selected from groups I-B, II-B, IV-B, V-B, VI-B, VII-- B, and VIII of the Periodic Table, and electrolytically depositing on the resulting substrate a metallic plate having a flex strength that is not greater than either cohesive strength of said substrate or the adherent bond strength of the metallic plate to said substrate.

27. The method of claim 26 wherein aromatic or aliphatic amines are present in the electrolytic bath in an amount sufiicient to produce embrittlement of the electrolytically deposited metal plate.

28. The method of claim 26 wherein a glycol is present in the electrolytic bath in an amount suificient to produce embrittlement of the electrolytically deposited metal plate.

29. The method of claim 26 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding fine inert solid particles, of less than 5 microns, in the metal plate.

30. The method of claim '29wherein fine inert particles are co-deposited with the electrolytic metal plate.

31. The method of claim 29 wherein the metal plate is nickel.

32. The method of claim 29 wherein the substrate is a plastic.

33. The method of claim 26 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

34. The method of claim 33 wherein the microscopically resolvable network of cracks is produced by conducting the electrolytic metal deposition in an electrolytic bath having a high chloride ion content of 150-500 g./l. nickel chloride.

35. The method of claim 33 wherein nicotinic acid is present in the electrolytic bath in an amount suflicient to produce microscopically resolvable cracks in the electrolytically deposited metal plate.

36. The method of claim 33 wherein the metal plate is nickel.

37. The method of claim 33 wherein the substrate is a plastic.

38. A method according to claim 1 for applying an adherent metal coating to a nonmetallic substrate comprising treating the substrate surface with an acidic solution so as to produce an adsorbing surface containing very small holes, pores, or channels therein, activating the thus treated substrate by subjecting it to a metal salt solution, subjecting the thus activated substrate surface to an electroless metal solution to deposit a metal coating thereon, and thereafter electrolytically depositing on said metal coating, a metallic plate having a flex strength that is not greater than either the cohesive strength of said substrate or the adherent bond strength of the metallic plate to said substrate.

39. The method of claim 38 wherein the acidic solution is selected from the group consisting of H 50 CrO H PO and mixtures thereof.

40. The method of claim 38 wherein the acidic solution is a mixture of H SO and CrO 41. The method of claim 38 wherein aromatic or aliphatic amines are present in the electrolytic bath in an amount sufiicient to produce embrittlement of the electrolytically deposited metal plate.

42. The method of claim 38 wherein a glycol is present in the electrolytic bath in an amount sufficient to produce embrittlement of the electrolytically deposited metal plate.

43. The method of claim 38 wherein the treated substrate is sensitized with a reducing salt prior to activation with said metal salt solution.

44. The method of claim 43 wherein the reducing salt is stannous chloride.

45. The method of claim 38 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding fine inert solid particles, of less than 5 microns, in the metal plate.

46. The method of claim 45 wherein fine inert particles are co-deposited with the electrolytic metal plate.

47. The method of claim 45 wherein the metal plate is nickel.

48. The method of claim 45 wherein the substrate is a plastic.

49. The method of claim 38 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

50. The method of claim 49 wherein the microscopically resolvable network of cracks is produced by conducting the electrolytic metal deposition in an electrolytic bath having a high chloride ion content of 150-500 g./l. nickel chloride.

51. The method of claim 49 wherein nicotinic acid is present in the electrolytic bath in an amount suflicient to produce microscopically resolvable cracks in the electrolytically deposited metal plate.

52. The method of claim 49 wherein the metal plate is nickel.

53. The method of claim 49 wherein the substrate is a plastic.

54. The method of claim 38 wherein the treated substrate is activated with a solution of Li PdCl in methanol and thereafter subjected to electroless metal plating.

55. The method of claim 54 wherein the activated substrate is treated with a solution of NaH PO in water prior to being subjected to electroless metal plating.

56. The method of claim 54 wherein the substrate is treated with a solution of CrO and H 80 57. The method of claim 54 wherein said flex strength of the electrolytically deposited metallic plate is provided by occluding therein fine inert particles co-deposited with the electrolytically deposited metal plate.

58. The method of claim 57 wherein the metal plate is selected from the group consisting of nickel and chromium.

59. The method of claim 57 wherein the substrate is a plastic.

60. The method of claim 54 wherein said flex strength of the electrolytically deposited metallic plate is provided by producing therein a microscopically resolvable network of cracks.

61. The method of claim 60 wherein the microscopically resolved network of cracks is produced by conducting the electrolytic metal deposition in an electrolytic bath, having a high chloride ion content of 150-500 g./l. nickel chloride.

62. The method of claim 60 wherein nicotinic acid is present in the electrolytic bath in an amount sufiicient to produce microscopically resolvable cracks in the electrolytically deposited metal plate.

63. The method of claim 60 wherein the metal plate is selected from the group consisting of nickel and chromium.

64. The method of claim 60 wherein the substrate is a plastic.

References Cited UNITED STATES PATENTS 3,582,452 6/1971 Britten 161213 OTHER REFERENCES M. Matsunaga et al., Adhesion of Electrodeposits to Plastics, Metal Finishing, November 1968, 66 (11), pp. -84.

JOHN H. MACK, Primary Examiner W. I. SOLOMON, Assistant Examiner US. Cl. X.R. 29-195; 161-213 UNITED STATES PATENT OFFICE CERTIFICATE OF CORREQTEUN Patent No. 3,681,209 Dated August 1, 1972 Inventor) Donald H. Campbell et al It is certified that error appears in the above-identified patent and that said Letters Patent. are hereby corrected as shown below:-

Column 6 line 25, "SnC1 .I-I O" should be ---SnCl .2H O--. 1

Column 6 line 28, "19/." should be -lg/l-. Column 10, line 23, "prepalted" and "palted" should be -prepla1 ed-- and ---plated---', respectively. Column 11 line 65 "phosphorous" should be phosphorus. .Column 14, line 24, "particles codeposited" shouldlbe ---p artioles of less than 5 microns, co-

deposited---.

Signed and sealed this 19th day of December 19 72.

(SEAL) Attest:

EDWARD M.FLETGHER,JR. ROBERT GOTTSCHALK At-testing Officer Y 1 Commissioner of Patents 

